I've recently needed to reprogram my trusty little time-lapse camera trigger, which is based on the ATtiny85 microcontroller and found out that the tutorial I followed last time isn't quite complete. So I've decided to create a step-by-step guide on how to program ATtiny85 using an Arduino Nano and the Arduino IDE, mostly as a handy future reference.

Step 1 - Build the circuit:

The image blow shows the wiring. Our goal is to program the ATtiny85 to blink the green LED. Note that the red LED is for diagnostics only, it's so-called heartbeat that indicates whether Arduino has been correctly set up as a programmer, we will talk about that later...